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#21
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What Autolite plugs running in SM heads
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#22
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NGK-8's also run them in my E-heads too.
GT |
#23
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Best Plugs.
I've tried all different plugs in my 1965 tripower and the NKG XP 5'S run the best so far.
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#24
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Thanks yeah 8’s didn’t work out for me had to go to NGK-9’s. Cooler plug. As you know
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#25
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Quote:
The JCY18s were a 2 piece electrode and it was not a good feeling to look at a flopping around pug wire and a hollow insulator. You could literally hear the difference when the Accel plugs were put in. I did that comparison thread on race plugs awhile back. While the Champion was the least robust of the plugs, I found nothing wrong with it. The NGK had the thickest electrode. Autolight was OK too. |
#26
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Quote:
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Jeff |
#27
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Hello!
I use a AC45 on my 9.2 comp 455" with Swedish 95 oktan. On my 9.7 comp 455" and Swedish 98 oktan I use AC43. Both pluggs acted similar to the engine. Thank You fron S.F. in Sweden. |
The Following User Says Thank You to S.F. For This Useful Post: | ||
#28
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I have AC 43s' in my signature .030 over 455 with zero problems.
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1979 Trans Am WS-6 .030 455 zero decked flat pistons 96 heads with SS valves 041 cam with Rhoads lifters 1.65 rockers RPM rods 800 Cliffs Q Jet on Holley Street Dominator ST-10 4 speed (3.42 first) w 2.73 rear gear __________________________________________________ _______________________________ 469th TFS Korat Thailand 1968-69 F-4E Muzzle 2 |
#29
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When these engines were initially built and released to the public we had higher octane and lead along with i believe dirtier fuel than now, so the engineers specified a plug with a heat range that would cook off deposits
Now fuel is cleaner no lead the plug does not need to be as hot to stay clean and combine that with lower octane the original heat specs are not as appropriate and can lead to detonation pre'ignition
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If your not at the table you're on the menu A man who falls for everything stands for nothing. |
The Following User Says Thank You to Formulas For This Useful Post: | ||
#30
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sorry if this is something of a small tangent from the last reply;
I believe that "45" was the heat range all Pontiac 400's used from 1971 through to 1979; The plug changed with the cylinder head revisions, but the heat range stayed the same; Quote:
When you add in thicker head gaskets, and multiple valve relief pistons, the compression tends to dip further yet... So all 1969-1970 400's (except for the RAIII and 1970 engines with #12 heads) made 9.4:1 compression; I believe that for 1971 & 1972 (I don't have the source handy) the compression for 400's was 8.4:1; I believe that the compression for 400' s in 1973 & 1974 was 8.2:1; It's been widely published that 1975 & 1976 engines all made 7.6:1 compression; I believe also that all 400's made after 1976 (except for the W72) also made 7.6:1 compression. Which is all to say that PMD used with 9.4:1, 8.4:1, 8.2:1, & 7.6:1 engines one version or another of the 45 heat range for spark plugs; R45S, R45TS, R45TSX ect, ect... This is why so many people use a 45. What I have been trying to point out is that the (relatively) few engines from 67-70 that exceeded 9.4:1 used a step cooler plug... Then GM confused matters by discontinuing the 44 heat range and superseded it with the 45 heat range; Then all of a sudden (some of you might have to dig back into your memories for this) people were saying that these older engines couldn't run unleaded pump gas... which was probably because the compression and gasoline required a cooler plug than the commonly spec'd 45.
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1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
#31
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When I run the nominal numbers (.020 deck, .039 gasket, 75CC chamber, 6CC piston dish) I get 9.64 compression for a '69 400. Take deck to .010" and compression goes to 9.85.
I'd bet the actual compression ratio of the early 400s was in the 9.55 to 9.8:1 range. The 10.5:1 was blueprint best case. I have been noticing that the R45S were almost bone white with AFRs in the 14.x-13.x during cruise. Which I thought was odd that the plugs would be that clean when running a double pumper with 70/79 jets and 64 PVCR.... E10 93 octane. Looks like I'll be moving to the XR5s. Will moving to cooler plugs allow the curve to come in a bit quicker? I'm all in by 3500 RPM. Its an older build in a hot climate and I don't want to set the tune on kill.
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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 |
#32
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I'm sorry my SM headed mot has autolite AR3933's
My iron heads are autolite AR133 AR134S can't remember without looking at the car GT |
#33
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Thanks so the autolite 3933 where ok, for me. Before I made change to NGK 9.
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#34
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Not trying to hi-jack OP's thread but do have an NGK question. I got my NGK's from Butler for my 428 with 6X-4 heads. Gave them my engine specs and they sent me some NGK plugs UR45IX (iridium). Have not installed yet due to health issues being treated now. I was checking out these plugs online and found several sites showing the UR45 plugs being equivalent to AC R43, ACR44, AC R45, and ASC R46. That's a wide span of heat ranges. Anyone have a better idea of how hot or cold these plugs are? I have used the AC 44 heat range for most of the my cars and AC 43 for running local drag race tracks. I hope these NGK's are closer to the 43-44 heat ranges instead of closer to the 45-46 heat ranges. Thanks!
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"No replacement for displacement!" GTOAA--https://www.gtoaa.org/ |
#35
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Used R44 in my RAIV motor gapped 0.45 with my DUI HEI
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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